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•Extrapyramidal Motor System

• Descending extrapyramidal paths receive

input from other parts of motor system:

• From the cerebellum

• From the basal ganglia or “corpus striatum”

•Basal Ganglia or “Striatum”

• Caudate & putamen get input from cortex, thalamus & substantia nigra, a midbrain motor area

• They send commands to globus palliduswhich sends them on to the motor portions of thalamus & brainstem

• Very interconnected system with lots of feedback loops

•Basal Ganglia or Striatum

• Interconnected set of nuclei (gray matter) buried within the cerebral hemispheres that have primarily motor functions

• Best known components:• Caudate nuclei (“tail shaped nuclei”)

• Putamen (“seashell”)

• Globus pallidus (“pale globe”)

• Connect with other motor regions in cortex, thalamus, and brainstem

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•Functions

• The basal ganglia are important for:

• Initiating or starting motor programs – often multiple programs at once

• Inhibiting undesired movements; terminating voluntary movements

•Parkinson’s Disease (paralysis agitans or shaking palsy)

• About 1% of those over 50 have PD (~ 1,000,000 total in US; 60,000 new cases/yr; 90% cases occur after age 60)

• Progressive deterioration of DA input to basal ganglia- the “nigrostriatal pathway” from substantianigra in midbrain to the “striatum”in forebrain

• We lose about 4% of those DA neurons/decade, but those with PD have accelerated loss (70% or more gone)

• Results in difficulty initiating movements & tremor

PD vs normal SN

Normal # of DA cells vs PD

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• The nigrostriatal

path sends DA messages from

the substantia

nigra to the basal ganglia.

•Classic PD Symptoms• Worsening bradykinesia (slowing of

movement) & akinesia (loss of movement)

• Rigidity (too much muscle tone); clumsiness, decreased postural stability so tends to fall

• “Pill-rolling” tremor-at-rest

• Reduction in movement is also seen in lack of

facial expression & blinking; shuffling walk without assoc. arm movements; soft, halting, monotone voice; slow blinks; small writing;

feeling stuck or frozen

•http://www.learner.org/vod/vod_

window.html?pid=1599• If video at above link does not immediately

appear, click on video # 31 in their list

Additional Video Options

• http://www.5min.com/Video/Understanding-

Parkinsons-Disease-29159696

• http://www.youtube.com/watch?v=o8lsjfjgAA

8

• The following gets a bit too detailed but does

talk about PD dementia

• http://www.uctv.tv/search-

details.aspx?showID=13686

•Possible Causes

• Environmental toxin of some sort

(industrial heavy metals, pesticides, “free radicals” currently under study)

• Genetics (especially in those who get atypical PD at an early age)

• Brain trauma may increase your risk

http://www.youtube.com/watch#playne

xt=1&playnext_from=TL&videos=8Lji02q

QKA0&v=UTImkp1e9Uk

One specific example of a toxin causing

immediate PD

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•Treatments• Increase DA production with l-dopa/carbidopa

(Sinemet)

• Problems: l-dopa induced dyskinesias and loss of effectiveness over time

• Others: DA agonist (bromocriptine/Parlodel or

pergolide/Permax, or newer, better Mirapex, Requip) or DA releasor (amantadine/Symmetrel)

• Eldepryl/Deprenyl (selegiline) to decrease DA breakdown and slow loss of neurons

• Anti-ACh drugs (Artane, Cogentin) can help restore chemical “balance” of basal ganglia

•Balance Between DA and ACh

•When Drug Therapy Fails

• When drug effectiveness declines, exp.

options include:

• Pallidotomy; thalamotomy (Michael J. Fox)

• Deep brain (thalamic) stimulation

• Transplant of DA producing cells

•PET Scan of DA Activity

Pallidotomy

http://www.youtube.com/watch?v=7bEKQGYH

zrc

http://www.youtube.com/watch#v=1DPw8NVi

I5I&feature=related

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•Alternative Surgery – Thalamotomy

• Damages motor

portion of

thalamus

• Michael J. Fox

had this surgery

done

Deep Brain Stimulation for PD

• http://www.youtube.com/watch#playnext=1&

playnext_from=TL&videos=XAUE164OopQ&v=

xejclvwbwsk

• http://www.youtube.com/watch#playnext=1&

playnext_from=TL&videos=XAUE164OopQ&v=

IOHtUzW02cg

•Parkinson’s Disease Update

• Although PD is thought of as a motor disorder, the decline in DA also produces cognitive and

emotional changes in some

• Major depression

• “bradyphrenia” (cognitive slowing); decreased attention

• “frontal lobe” symptoms (disinhibition of behavior, poor judgment and planning)

• Full-blown dementia in ~40-50% (associated with neuropathological sign called Lewy bodies)

• PD treatment, on the other hand, can produce hallucinations and other symptoms of psychosis